1. Field of the Invention
The present invention relates generally to a semiconductor manufacturing apparatus, and more particularly, to a cleaning probe adapted for use with a megasonic cleaning apparatus.
This application claims priority to Korean Patent Application 2004-79041 filed on Oct. 5, 2004, the subject matter of which is hereby incorporated by reference.
2. Description of Related Art
The fabrication of a semiconductor device of a wafer involves a complex sequence of individual processes. If particles are allowed to contaminate the surface of the wafer, pattern failures are likely to occur during subsequent processes in the fabrication sequence. These pattern failures are common causes for the ultimate failure of the semiconductor device.
Advances in fabrication and design technologies have allowed the production of semiconductor devices having finer patterns having smaller gaps between patterns sections. As pattern sizes have diminished and fabrication tolerances have been correspondingly reduced, smaller and smaller particles become potential problems. This trend places additional burdens on cleaning processes adapted to remove potentially contaminating particles from the semiconductor device fabrication environment. Yet, it is increasingly difficult to eliminate smaller and smaller particles using existing cleaning processes, because of relatively strong adhesion forces existing between the particles and the wafer surface.
The need for an improved wafer cleaning process has been recognized for some time now. Several previous attempts have been made to improve the effectiveness of conventional cleaning processes. Some of these methods provide a force to the surface of a wafer in order to overcome the strong adhesive force between the particles and wafer. One such previously proposed method uses a megasonic cleaning apparatus that applies megasonic waves to the wafer being cleaned.
In general, a megasonic cleaning apparatus includes a piezoelectric transducer configured to generate megasonic waves, and a cleaning probe configured to transmit the megasonic waves generated by the piezoelectric transducer onto the surface of the wafer through a cleaning fluid, (e.g., deionized water). The high frequency waves generated by the cleaning probe generate bubbles inside the fluid. As the bubbles impact and burst on the surface of the wafer, the resulting force—formed by the combination of bursting bubbles and fluid displacement (e.g., a directed fluid flow)—vibrate the particles and separate them from the surface of the wafer. This conventional method removes potentially polluting particles from the wafer surface safely and effectively. Indeed, conventional megasonic cleaning processes effectively remove particles from recessed regions of the wafer surface.
FIG. 1 illustrates a conventional cleaning apparatus and a graph illustrating the relative force applied by the conventional cleaning probe along the radial length of a wafer. The conventional megasonic cleaning apparatus illustrated in FIG. 1 is disclosed in U.S. Pat. No. 6,039,059.
Referring to FIG. 1, a conventional cleaning probe 20 contacts a cleaning fluid (not shown) which is uniformly distributed over wafer W. One end of cleaning probe 20 is connected to a piezoelectric transducer 10 and the opposite end of cleaning probe 20 extends over wafer W. Cleaning probe 20 typically takes the shape of a cylindrical rod having a cross section of uniform diameter. High frequency megasonic waves are generated by piezoelectric transducer 10 and transmitted through cleaning probe 20 to the cleaning fluid. The resulting formation and bursting of bubbles upon wafer W removes potentially polluting particles.
FIG. 1 also illustrates the relative force applied at various points across surface of wafer W by cleaning probe 20 through the cleaning fluid. As can be seen, the applied force varies with radial distance from the center of wafer W. That is, the force applied to the surface of wafer W at its outer edge portion is greater than the force applied to the center portions of the wafer.
In effect, the force imparted by the megasonic waves produced by the conventional megasonic cleaning apparatus is concentrated at the edge of wafer W, because much of the energy applied by piezoelectric transducer 10 to cleaning probe 20 dissipates along the length of cleaning probe 20 as it extends away from piezoelectric transducer 10. Given the conventional cleaning probe configuration, if the force of the megasonic waves induced by piezoelectric transducer 10 are increased in order to provide an adequate cleaning effect at a center portion of wafer W, a relatively large force is necessarily applied at the edge portion of wafer W. At some point, these large forces risk damage (e.g., pattern lifting) to components or surface layers formed on the edge portion of wafer W.